1. Technical Field
The present invention relates to a gas cartridge for supplying a fuel gas which is used for a strike tool of a gas nailer or the like for striking a fastener of a nail, a screw or the like by a combustion pressure of the gas.
2. Background Art
A strike tool for striking a fastener of a nail, a screw or the like by a combustion pressure of a gas is charged with a gas cartridge and the gas is supplied from the gas cartridge. In a normal case, a gas cartridge is provided with a multiple structure comprising an outer vessel (outer can), a gas charge vessel (inner bag), and an inner space formed between the two vessels. A liquefied fuel gas at inside of the gas charge vessel is injected by compressing to deform the gas charge vessel by utilizing a pressure of a compression gas at high pressure charged into the inner space.
Further, the outer vessel and the gas charge vessel of the gas cartridge having the above-described two chamber structure pressure charging apparatus are made of aluminum, particularly, the gas charge vessel is easy to be deformed by receiving a press force of the compression gas, the gas at inside is not permeated to outside, and therefore, a comparatively thin vessel which is easily deformable is preferred (JP-B2-2873691).
Meanwhile, according to the vessels of the multiple structure of the gas cartridge, the fuel gas at inside of the gas charge vessel is discharged to outside of the gas cartridge by pressing to crush to thereby recess to deform the gas charge vessel by the pressure of the compression gas charged to the inner space between the two vessels. Deformation of the gas charge vessel utilizing the pressure of the gas is free deformation, and therefore, there is a case in which the gas charge vessel is not uniformly deformed. That is, at an initial stage of deforming the gas charge vessel, a portion having a weak rigidity is recessed to deform, deformation of the portion is further promoted, and therefore, in a number of cases, only one portion is considerably recessed to deform.
Further, since an opening portion and a bottom portion of the gas charge vessel are highly rigid and difficult to be deformed, and therefore, a stress is concentrated on a portion excluding these portions, further, deformation is continuously progressed from an initially deformed portion which is deformed initially, and therefore, only one portion is considerably deformed. Therefore, a wrinkle or a fold is brought about at the portion, and a crack or a pin hole is produced. For example, as shown by FIG. 15, a bottom portion 12 of an inner bag 2 is pulled to an opening side, a stress is liable to be concentrated on a boundary portion 13 between the bottom portion 12 and a side face portion 10, and therefore, there is brought about a phenomenon that the bottom portion 12 is considerably deformed to fall down to the opening side. When a crack or a pin hole is produced at the gas charge vessel in accordance therewith, the compression gas is brought into the inner bag charged with a gas, and therefore, the pressure of the compression gas is relatively reduced and a gas charge vessel is not sufficiently compressed. Therefore, the fuel gas is discharged insufficiently, and a function thereof as a gas can is lost while the fuel gas remains. Abandoning the fuel gas before being sufficiently utilized not only deteriorates an operational efficiency of the strike tool constituting a drive source by the gas but also constitutes an economic loss.
In this way, according to the gas cartridge, both of the outer can and the inner bag are made of a metal, particularly, the inner bag is thin-walled, and therefore, there poses a particular problem that a crack or a pin hole is liable to be produced.